A light emitting diode (LED) is a semiconductor device, which emits different colored light driven by current. Semiconductor material consisting of a compound of the III-V family such as gallium nitride (GaN) has attracted widespread attention because of its wide bandgap, high luminous efficiency, high saturated electron drift velocity, high chemical stability, and huge potential in high brightness blue LED, blue lasers and other optoelectronic fields.
However, conventional LED devices have a problem of low luminous efficiency, which are only several percentage points before LED packaging. Large amount of energy is wasted inside LED devices, causing both energy waste and shorter service life. Therefore, improving the luminous efficiency is very important for LED devices.
Based on the above requirements, many ways of improving the luminous efficiency of LED have been applied to the LED device structure, such as the surface roughening method, metal reflecting mirror structure, etc. In a Chinese patent application (publication number CN1858918A), an LED with an omnidirectional reflector structure to improve the luminous efficiency is disclosed. However, in the method, a film structure including stacked high refractive index layers and low refractive index layers is required to be formed on a substrate. Therefore, the manufacture process of the method is complex.